Struct FirstSets 

pub struct FirstSets<'a, G> { /* private fields */ }

Collector of FIRST sets.

Implementations

impl<'a, G> FirstSets<'a, G>

where G: RuleContainer,

pub fn new(grammar: &'a G) -> Self

Compute all FIRST sets of the grammar.

We define a binary relation FIRST(N, S), in which N is related to S if the grammar has a production of the form N ⸬= α S β, where α is a nullable string of symbols.

We compute the transitive closure of this relation.

pub fn first_set_for_string( &self, string: &[Symbol], ) -> BTreeSet<Option<Symbol>>

Calculates a FIRST set for a string of symbols.

Trait Implementations

impl<'a, G> PredictSets for FirstSets<'a, G>

fn predict_sets(&self) -> &PerSymbolSets

Returns a reference to FIRST sets.